Effects of the soy isoflavones, genistein and daidzein, on male rats’ skin

Introduction
Genistein and daidzein are typical soy isoflavones with known estrogenic properties to provide protection against skin ageing in postmenopausal women and female rats. However their effect on male skin was very rarely studied.

Aim
This study was designed to evaluate the effect of a mixture of genistein and daidzein on male rats’ skin.

Material and methods
Male rats were administered this mixture in a dose of 2 or 20 mg/kg body weight (bw) per day for 5 days weekly mixed with regular rat chow, from prenatal life until sexual maturity. The female and male rats of the control group received regular rat chow. The skin epidermis thickness, number of fibroblasts in the dermis and diameter of collagen fibers in the dermis were measured using morphometric assay. The isoflavone effects on activities of antioxidant enzymes, lipid peroxides, and glutathione concentration in the skin were measured with commercially available kits.

Results
The thickness of the skin epidermis and collagen fibers in the dermis and amount of elastic fibers were significantly greater in the isoflavone-treated groups. Isoflavones significantly decreased catalase activity in the skin homogenates and at a higher dose inhibited lipid peroxides formation.

Conclusions
Our results provide further support for the contribution of isoflavones to defence mechanisms against oxidative stress in the skin and suggest that genistein and daidzein supplementation may provide protection against skin ageing in males.